Consider the following - the way it is today:
Uninsured bum#1 contracts TB, and brings it back to his cardboard box down by the river under the bridge, and proceeds to cough and sneeze all over uninsured bums#2 thru #10 huddled around a flaming trash can. After a month of infecting his buddies (and NOT being seen by a Dr.), Bum#1 finally keels over with a collapsed lung or something, and someone calls the cops, who call an ambulance, and haul him to the ER. Bum#1 is admitted to the hospital after surgery to get that lung pumped up, and spends the next 2 weeks in the isolation ward, which now also contains uninsured bums#2 thru #10 who he infected but didn't see a Dr. either. But many with Insurance are so happy they didn't have to pay for all these 'worthless' sick and hospitalized bums now costing (us) thou$and$ or more a day for in-hospital care.
Now consider the following with Universal (Single Payer) Healthcare:
Universally covered bum#1 contracts TB, and brings it back to his cardboard box down by the river under the bridge, and proceeds to cough and sneeze all over uninsured bums#2 thru #10 huddled around a flaming trash can. After a few days of symptoms, Bum#1 goes to the clinic, is diagnose with TB, and is sent back to his cardboard box with antibiotics and the knowledge that he has TB. He tells bums#2 thru #10 that he has TB, and they all go to the clinic, and they are given antibiotics and sent back to their cardboard boxes. In 2 weeks none of the bums are contagious, and the TB is under control. But many paying taxes that guarantee healthcare to these bums are still unhappy they had to pay for 10 clinic visits and a bunch of antibiotics, except it only cost a couple hundred bucks each to stop the TB, instead of many thou$and$ to hospitalize 10 bums, not to mention any other people they infected.
And so many who are insured, pay taxes and vote (and also could catch TB passed into gen-pop by these bums) still argue that Universal Healthcare will cost more, create shortages, and lower the level of care. Either example above still costs the insured / tax payer for the bum's care, so why not pick the healthier, more economical and more responsible alternative since we're paying for them either way?